1. Field of the Invention
The present invention relates generally to dynamo-electric machines with laminated rotors and stator cores, and more particularly to lamination constructions in which stator teeth and rotor slots have relative dimensions such as to provide improved output for a given size machine.
2. Description of the Known Art
Arrangements are known for improving efficiency or power output of dynamo-electric machines through the provision of certain slot distributions in either a stator or rotor core element of the machine, e.g. U.S. Pat. No. 4,566,179 (Jan. 28, 1986), or by creating a prescribed variation of magnetic flux through a pole of the machine stator relative to the ampere-turns of the pole such as in U.S. Pat. No. 4,209,720 (Jun. 24, 1980). There has not, however, been available a machine lamination construction by which the operating efficiency of a dynamo-electric machine having a stacked laminated stator and/or rotor is improved by a prescribed ratio of inner diameter to outer diameter for the lamination. Also, there has not been available a lamination construction by which the ratio of flux density in a tooth portion of the lamination to flux density in a yoke portion of the lamination can be increased over that obtained conventionally, and, as a result, yield greater output or operating efficiency for the machine.
Rotors formed of a stack of laminations having closed slots equally spaced from one another about the periphery of each lamination are known from, for example, U.S. Pat. Nos. 2,794,138 (May 28, 1957) and 3,401,280 (Sep. 10, 1968), both having been assigned to the assignee of the present invention.
Such rotors are ordinarily used in inductive AC motors, wherein conducting members which extend axially along the rotor through aligned slots of the stacked laminations interact with a rotating magnetic field created in an air gap between the outer circumference of the rotor and the inner circumference of the machine stator. Windings embedded in stator slots between radially inwardly projecting teeth of the stator, adjacent the air gap, are connected to the AC mains, and the stator winding conductors pass through a certain order of the stator slots so as to cause magnetic flux in the air gap to rotate in synchronism with the frequency of the AC mains.
Conventionally, each of the rotor slots is constricted between its top and bottom parts in the radial direction, to form a so-called neck portion of the slot. Such closed slot rotors ordinarily have the slots in each of the rotor laminations formed with an inverted V shaped edge at the upper boundary of the top part of the slot, with the center of the V creating a narrow bridge part between the upper boundary of the slot and the outer circumference of the lamination. Understandably, such bridge part presents difficulties in machining of the closed slots at the peripheries of the rotor laminations.